Rename Word to reg16_t.
Emu: DataBus

Convert from the fixed AddressBus to a templated DataBus
SDL: Switch over to opengl for drawing.

OS X software path was painfully slow.
Galaga: Update render loop.
m6502: Hook up IRQ line
Emu: Replace radix tree with a small hash table
NES: Add MMC3 mapper.

Add the MMC3 mapper, found in a lot of Nintendo cartridges.
Cpu: m6502 updates for test rom
Cpu: Create NES specific CPU

Subclass the m6502 to create the NES specific (n2a03) variant.
NES: New rendering

More accurately emulate the behavior of the 2005h/2006h registers.
Back down on per-pixel rendering until I can work out the timing issues
with updating the horizontal scroll mid-scanline.